JPH07145407A - Production of flat powder for design coating material - Google Patents

Abstract

PURPOSE:To produce flat powder for a design coating material having a smooth surface and circumference, high brightness and hardness and small grain size at a good yield. CONSTITUTION:A molten alloy consisting of the compsn. expressed by general formula Al110-a-bMaXb (where M is one or 2 kinds of elements selected from Co, Ni and Cr, X is one or 2 kinds of elements selected from among Y, La, Ce, Sm, Nd, Ca, Mn [mischmetal] and a, b are 2<=a<=20, 1<=b<=15 by atm.%) is atomized to obtain amorphous raw material powder. The powder of <=20mum grain size is preferably selected from this raw material powder and is flattened by ball milling or stamp milling, by which the flat powder for the design coating material is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a flat powder for design paints made of an amorphous aluminum alloy.

[0002]

2. Description of the Related Art Conventionally, a metal powder has been used as a pigment for paints in order to improve the corrosion resistance and weather resistance of a coating film and to obtain an appearance with metallic luster. That is, when metal powder is mixed with a resin for paint and applied by a brush coating method, a spray method, etc., the powder is laminated in parallel with the coating surface due to the surface tension generated when the resin is cured (this is called a leafing phenomenon), A continuous film is formed to shield the material from the outside air, and good corrosion resistance and weather resistance are obtained, as well as a beautiful appearance having a metallic luster. It is generally said that the shape of such a metal powder is preferably a flaky shape in order to improve the occurrence of the leafing phenomenon.

As the above-mentioned pigments for paints, especially pigments for decorative paints, flat powders made of pure aluminum are generally used. This aluminum powder is made into a particulate raw material powder from molten aluminum by an air atomizing method or an inert gas atomizing method, and the raw material powder is pulverized in a ball mill or a stamp mill to be finely pulverized and extended by shearing force. It is physically flattened.

Further, Japanese Patent Application Laid-Open No. 1-287 by the present applicants
In No. 209, a molten alloy of an alloy capable of forming an amorphous phase is caused to flow out of a nozzle, and a gas is sprayed onto the molten metal to generate droplets of the molten metal. Or, on the surface of the horn-type rotary cooling body, by colliding the droplets before solidifying to rapidly solidify,
A method for directly producing a flat powder from a molten metal is disclosed.

On the other hand, in recent years, been found amorphous alloys of aluminum-based large number, for example, in JP-A-1-275732, Al _a M _b X _c based amorphous alloys have been disclosed.

[0006]

However, since crystalline raw material powder such as atomized powder of pure aluminum generally has low strength, when flattened in a ball mill or a stamp mill, the raw material powder is crushed or cracked. hand,
Irregularities were generated on the periphery and the surface, and good reflectance and gloss were not obtained when it was made into a paint. Further, since the flat powder has a low hardness, there is a problem that the powder is bent when the coating material is stirred and the reflectance is further lowered.

[0007] Further, as the flat powder for the design paint, it is said that a powder having a small particle size, for example, a powder having a particle size of about 50 µm or less is preferable in view of coatability and coating strength. In the method disclosed in, the fine droplets of the molten metal solidify in a spherical shape before colliding with the surface of the rotary cooling body. Further, the powder having a large particle size which is solidified without coming into contact with the rotary cooling body lacks the rapid cooling effect and is unlikely to become amorphous. Therefore, there is a problem that the yield of fine flat powders made of an amorphous alloy is low.

Therefore, in order to obtain an amorphous alloy powder having a fine particle diameter, it is necessary to adopt an alloy composition which becomes amorphous only by atomizing.
The Al _a M _b X _c alloy composition disclosed in No. 5732 did not necessarily become amorphous just by atomizing.

Therefore, it is an object of the present invention to provide a method for producing a flat powder for a design paint, which has a smooth surface and surroundings, a high gloss and hardness, and a small particle size with a high yield.

[0010]

In order to achieve the above object, the method for producing a flat powder for a design paint according to the present invention comprises a general formula Al _100-ab M _a X _b (where M is Co, Ni or Cr). One or more selected elements, X is Y, La, C
e, Sm, Nd, Ca, Mm is one or more elements selected from [Misch metal], and a and b are atomic%
2 ≦ a ≦ 20 and 1 ≦ b ≦ 15. ) Atomizing the molten alloy having the composition shown in) to obtain an amorphous raw material powder, and a step of flattening the raw material powder by ball milling or stamp milling.

The present invention will be described in more detail below. The reason why the alloy composition is limited as described above in the present invention is that the alloy composition is limited to a composition that is more likely to be amorphous so that the alloy becomes amorphous only by atomizing. That is, as described above, the fine droplets of the molten metal solidify before colliding with the surface of the rotary cooling body, so in order to obtain an amorphous alloy powder having a fine grain size, This is because it is necessary to have a composition that can become amorphous only by atomizing without colliding with the rotary cooling body. In the present invention, the amount of M is less than 2 atomic% or exceeds 20 atomic%,
And, if the amount of X is less than 1 atom% or exceeds 15 atom%, it is difficult to form an amorphous phase only by atomizing, which is not preferable.

There is no limitation on the method of atomizing the molten alloy to obtain the amorphous raw material powder, and various commonly used atomizing methods such as the air atomizing method and the inert gas atomizing method can be applied. For example, argon, helium, nitrogen, air, or a mixed gas thereof is preferably used as the injection gas, and the injection gas pressure from the atomizing nozzle is preferably 20 kg / cm ² or more.

In the present invention, among the powders obtained by atomizing, it is preferable to classify powders having a particle size of 20 μm or less as raw material powder, and powders having a particle size of 5 to 15 μm are preferable. When the particle size of the raw material powder exceeds 20 μm, the particle size of the finally obtained flat powder becomes too large, which is not preferable. Further, the shape of the powder at this time is more preferably spherical so that the shape of the powder when flattened becomes a round and uniform shape.

The reason why the particle size is set to 20 μm or less is based on the following calculation. That is,
If the spherical powder is crushed and processed into a disk-shaped flat powder having a thickness of 2 μm, the relationship between the diameter D _{o of the} spherical powder and the diameter D _d of the flat powder is shown in Table 1 below if the volumes of both are equal.
Is the street.

[0015]

[Table 1]

Therefore, in order to obtain a flat powder having a particle size of about 50 μm or less, which is considered to be preferable as a flat powder for a decorative coating, it is necessary to flatten the powder having a particle size of about 20 μm or less.

The particle size thus obtained, preferably 20 μm
By flattening the raw material powder having a particle diameter of m or less by ball milling or stamp milling, a flat powder for a design coating can be obtained. The size and shape of the ball mill device,
The ball diameter, rotation speed, processing time, etc. are not limited, and may be appropriately selected depending on the amount of raw material powder, the target thickness, and the like. The stamp mill device is also not particularly limited, and various types can be used. In addition, it is preferable to flatten the thickness of the finally obtained powder to 3 μm or less, and more preferably 0.3 to 1 μm.

In the ball mill processing or stamp mill processing, it is preferable to use a lubricant such as stearic acid or oleic acid. This makes it possible to keep the luster of the powder good, prevent the powders from adhering to each other, and make the particle size of the flat powder uniform. The amount of lubricant used is preferably about 0.01 to 5% by weight with respect to the amount of powder. As the organic solvent that dissolves the lubricant, mineral spirit, acetone, toluene or the like may be used.

The thus obtained flat powder for design paint is
It is preferably a flat powder having a particle size of 50 μm or less and a thickness of 3 μm or less and having a substantially circular shape, and can be used as a pigment in various water-soluble solvent paints and organic solvent paints.

[0020]

As an aluminum-based amorphous alloy, for example, Al _a M _b X _c disclosed in JP-A-1-275732 is used.
Although many alloys such as alloys are known, the alloy having the composition of the present invention is characterized by having a higher amorphous forming ability than other aluminum-based amorphous alloys as described above. For this reason, it is possible to make it amorphous by only atomizing without colliding with the rotary cooling body, and as a result, it is a powder of a fine particle size that solidifies in the space during atomization. Can also be amorphous.

That is, in the present invention, by limiting the composition of the alloy as described above, it is possible to obtain an amorphous raw material powder having a small particle size in a high yield. Further, while the hardness of pure aluminum powder is HV20 or less, HV2
A raw material powder having a high hardness of 00 or more can be obtained. Further, it is possible to obtain a powder having sufficient luster and corrosion resistance as a design coating powder.

Further, since the above amorphous raw material powder is excellent in workability, it does not break or crack even if it is subjected to ball milling or stamp milling, and it is flattened while keeping the surface and the periphery smooth. Can be converted. For this reason,
It is possible to obtain a flat powder having a uniform shape, high gloss and high reflectance.

[0023]

【Example】

Examples 1 to 4 and Comparative Examples 1 to 7 Alloys or aluminum having various compositions shown in Table 2 were melted in a high-frequency melting furnace, and in a high-pressure gas atomizer, Comparative Example 2 had a pressure of less than 20 kg / cm ² , and others had a pressure of 40.
Atomization was performed by spraying nitrogen gas of kg / cm ² . As a high-pressure gas atomizer, Japanese Patent Application Laid-Open No. 1-2870
An atomizing device described in No. 9 without an umbrella-shaped rotary cooling body was used. The molten metal temperature during spraying was 800 ° C. in Comparative Example 5, and 1100 ° C. in other cases. From the powder thus obtained, a spherical powder having a particle size of 20 μm or less was classified to obtain a raw material powder.

Next, 50 g of each raw material powder was added to the container inner diameter 16
It is put into a stainless steel ball mill (made by Irie Shokai Co., Ltd.) having a height of 0 mm and a height of 160 mm, and fine powder is obtained by finely pulverizing stearic acid dissolved in mineral spirits for 12 to 24 hours at a rotation speed of 60 rpm as a lubricant. Obtained. The balls are 3/4, 5/8, 1/2,
3/8 inch ones were used in combination.

X-ray diffraction was performed on each of the above raw material powders before and after ball milling to examine the powder structure. Further, each flat powder was observed with a scanning electron microscope to compare the shape and gloss. The results are shown in Table 2. Further, a scanning electron micrograph of the flat powder of Example 1 at a magnification of 500 is shown in FIG. 1, and a scanning electron micrograph of the flat powder of Comparative Example 1 at a magnification of 500 is shown in FIG.

[0026]

[Table 2]

From the results shown in Table 2, it was found that when the alloys having the compositions shown in Examples 1 to 4 were atomized and classified, completely amorphous powders were obtained. On the other hand, Comparative Examples 1 and 3
When atomizing the alloy having the composition shown by ~ 7,
It was not possible to obtain a completely amorphous powder. Also,
In Comparative Example 2, an alloy having the same composition as in Example 1 was atomized with the injection gas pressure being less than 20 kg / cm ² , but in this case also, completely amorphous powder could not be obtained. It was

Then, when the amorphous powders of Examples 1 to 4 were ball-milled, as shown in FIG. 1, it was possible to obtain flat powders having smooth surfaces and glossy surfaces. On the other hand, when the crystalline powder as in Comparative Example 1 or the powder in which crystalline and amorphous are mixed as in Comparative Examples 2 to 7 is ball-milled, the periphery of the powder is cracked as shown in FIG. Or, unevenness was generated on the surface, and it was not possible to obtain a flat powder having a good shape and gloss as in Examples 1 to 4.

The flat particles thus obtained in Examples 1 to 4 had an average particle size of 20 to 30 μm and an average thickness of 0.5 to 2.0 μm. In addition, Examples 1 to 4
The yield of the finally obtained flat powder in
It was 5%.

[0030]

As described above, according to the present invention,
By atomizing a molten alloy having a specific composition into an amorphous raw material powder, and subjecting this raw material powder to ball milling or stamp milling, the circumference and surface are smooth, and the gloss and hardness are high and the particle size is small. The flat powder for decorative paint can be produced in good yield.

[Brief description of drawings]

FIG. 1 is a photomicrograph showing the particle structure of a flat metal powder for a decorative coating produced by the method of the present invention.

FIG. 2 is a micrograph showing a particle structure of a flat metal powder for a design coating material manufactured by a conventional method.

Claims (3)

[Claims] 1. The general formula Al _100-ab M _a X _b (provided that M
Is one or more elements selected from Co, Ni and Cr, X is one or more elements selected from Y, La, Ce, Sm, Nd, Ca and Mm [Misch metal] And a and b are 2% a ≦ 20 and 1% b ≦ 15 in atomic%. ) Atomize the alloy melt with the composition shown in
A method for producing a flat powder for a design coating, comprising: a step of obtaining an amorphous raw material powder; and a step of flattening the raw material powder by ball milling or stamp milling. 2. The method for producing a flat powder for a design paint according to claim 1, wherein a powder having a particle size of 20 μm or less is collected from the raw material powder and subjected to the ball mill processing or the stamp mill processing. 3. The method for producing a flat powder for a design coating according to claim 1, wherein the raw material powder is flattened to have a thickness of 3 μm or less.